Machine tool drive



y Nov. 10, 1953 w. w. POTTER ET AL MACHINE TOOL DRIVE 4 Sheets-Sheet lOriginal Filed Mag.T 26, 1944 W. W. POTTER ET AL Nov. 10, 1953 MACHINETOOL DRIVE 4 Sheets-Sheet 2 Original Filed May 26, 1944 NOV- 10, 1953 nw. w. POTTER ET AL 2,653,404

MACHINE TOOL DRIVE Original F'led May 26, 1944 4 Sheets-Sheet 5 5 A. d*FULLER Nov. 10, 1953 w. w. POTTER ET AL MACHINE TOOL DRIVE 4Sheets-Sheet 4 Original Filed May 26, 1944 Patented Nov. 10, 1953 UNITEDSTATES PATENT OFFICE MACHINE TOOL DRIVE William Wallace Potter andAlfred Joseph Fuller,

Pawtucket, R. I., assignors to Niles-Bement- Pond Company, WestHartford, Conn., a corporation of New Jersey 3 Claims.

The present invention relates to a change-speed mechanism applicable tomachines having a movable part or member to be driven selectively atdifferent speeds and has particular application to machine tools andespecially those machine tools having a rotatable spindle and acooperating reciprocating part or carriage movable to and fro relativeto the spindle, the latter supporting the work-piece and said carriagesupporting a tool holder, or vice versa.

This application is a division of application Serial No. 767,460 filedAugust 8, 1947 now Patent No. 2,561,753, which is a division ofapplication Serial No. 537,490 iiled May 26, 1944 now Patent No.2,455,876.

In machine tools, the rotative movement of the spindle is termed thespeed and the movement of the reciprocating part or carriage or slide isdivided into fast or idle motion and slow or Work performing motion, thelatter motion being termed the feed rThe object of the present inventionis the provision of a very simple, less expensive, novel and efcientchange-speed mechanism that includes a device for obtaining at leastfour speed-changes of the spindle and a device for obtaining fast motionand at least three feed-changes of the slide and carriage in a mannerwhich will insure that no damage will be done to the machine, or theinstrumentality operated by the machine, or to the work-piece, beingoperated on or by the machine.

Another object of the invention is the provision of means in the spindlespeed-change mechanism .for changing the speed range of the machine,independently of the speed-change device or the usual hand-change gears,whereby the range of the machine may be increased or decreased fordifferent classes of materials being worked-upon, thus greatly wideningthe capacity and use of the machine.

While speed-change and feed-change devices are numerous in the art, itis believed that the construction and organization of parts of thepresent invention is novel, and since its utility has been proven, itconstitutes a valuable improvement in the art.

'The invention, therefore, resides in that which is shown and describedand particularly pointed out in the appended claims.

In the drawings which show preferred embodiment of the invention as nowdevised and used- Figure l is a front elevation of a machine tool, ofthe automatic turret type, to which the invention is applied as oneillustration of its use;

Figure 2 is an end view of the head-stock of the machine tool andlooking from the left hand end of Fig. 1, with a portion of the casingbroken away to illustrate the gear assembly and the headstock of themachine;

Figures 3 and 4 illustrate a lay-out of the gearing and are to be readtogether, Figure 3 being the drive between the source of power for themachine and its spindle 2l in which drive the spindle speed-changemechanism of this invention is interposed and Figure 4 being the drivebetween the spindle 2l and the slide or carriage 23 or 25 in which drivethe feed-change mechanism of this invention is interposed.

Throughout the specification and drawings the like characters andreferences denote similar and like parts in the several Views. In orderthat a better understanding may be had of the present invention a briefdescription will now be given of the machine tool with which the presentinvention is illustrated as one example of its application.

The machine tool shown in Figure 1 is of the general pattern andorganization found in automatic turret lathes, in that it comprises aheadstock 20 in which is disposed and journalled a horizontal spindle2l, a gear drive from a source of power M to the spindle, thechange-speed mechanism of the present invention, a selective controldevice H2 is automatically, as well as manually by keys K, controllingthe operation of the machine, and the turret lathe further includes abed 24 disposed at one side of the headstock 20 and upon which theturret slide 23 is reciprocably mounted for movement longitudinally withrespect to the spindle and toward and away from the chuck 22 carried onthe outer end of the spindle and, also, upon which are mounted thecross-slides 25 disposed between the chuck 22 and the turret slide 23for reciprocatory movement at substantially right angles to the movementof the turret slide, the turret slide 23 being actuated by the cam |35which in turn is actuated by a feed shaft 39 from the spindle or spindledrive through a feed-change device and the cross-slide 25 beingactuated, preferably, by the movements of the turret slide toward andfrom the chuck.

As fully described and shown in the copending application abovementioned, the feed shaft 30, is driven from a feed drive, within theheadstock (see Figs. 2 and 4) to actuate the turret slide 23 and thecross-slides 25. The spindle 2l and the feed shaft 30 are revolved atdifferent speeds which are automatically selected, there being a drivingconnection between the spindle and feed Shaft by which the rate of feedcutting movement ofthe tool'L slides is controlled by the spindle speed.Also, the idle movements of the tool slides toward and from the work aredriven at a constant high speed; and the rotation of the spindle may bestopped, under certain conditionsxduring such high speed idle movementsof the tool slides, so that the workpiece Wiin the'fchuck 'will notrevolve in order that tool marks 'on the 'work piece,` will not occurdue to unintentional or accidental contact of the tools with the workduring their fast idle motion. Furthermoretheichangeispeed gearing, forvarying the rate of-A rotation fof: the spindle and of the feed shaft,lincludes the clutches which are under control vof aidogwheelhaving arelatively slow peripheralxrnotion, which.,op erates to bring intoaction power-operated`clutchshifting mechanism to instanteously'shiftlthe selected clutches. This/instantaneous shifting of 1. clutchesis also particularly-.useful Whereitiis desired'to increase: the'speedof. the spindlelto com- .pensatey for -reductionin .cuttingspeed Aof the`tools on-the worin-for instance, ias-the tool. proceeds from theworkpiece periphery..inwardly, thus enabling. more rapid productionvofwork by .-the machine under .certain conditions as.- where s facingcuts are ynovi/performed-simultaneously withothercuts.

Y With the aboveA -brief general description, the, i,detaileddescriptionv vof 'the improved mechanism A4employed byltheApresentv invention wi11;-now. pro- ..f,ceed.

:,.IHEADSTOCK l.Spin'dle'cmd spindle drive Withfreference particularlyto Figures l. and 2, the bed 24: of thev .machine is a..casting designed.tosupport and, in someinstances, .encloseits .--mechanism,-thehead-stock .end .20.'there'of being for-medi to provide acasing for fthepower-plant motors, transmission mechanism, including-fthe Y l.speed:and I f eedchange .clutches Iand ,their -selective-control .andnactuatingmeans.

yThe .spindle 2l is rotatably., mo,unted.in. the

clutch controlfmechanism 214, etc. .being .shown in'Fig-ure 4, while thezentiregearing in Figures 3 and 4 is shown inits assembled arrangementin -.-'Figure 2.

. With .particular reference .to Figures 2 and 3, it will be seen thatthere are two aligned rotatable shafts 36 and-31..mounted in suitablebearings in the heatstock frame 20.and that the driving gear L '35 iskeyedtoone endjof the shaft 36 which may be regarded asjthevspeedAinputl shaft and that 'the shaft'31 may berega'rded asthe-speed output'.'shaft Journaledin the headstock '20 in Ycooperative relationandparallel withithe aligned-'shafts -36 and V31A isa'rotatablefcountershaft# 38=Which` has rotatably mounted upon it fourclutches 39, 40, .4| .and 42 arranged -in two opposing pairs, each r'pair being served by a single sliding part or cone, respectively-'forinstance, clutch heads 39 and 5. 49 being served by the clutch cone 43and clutch heads 4| and 42 being served by the clutch cone .ff`44-ethus;when the clutch cones 43 and 44 are .engaged with anyone of their clutchheads, the f 'othenclutch headfof each pair is disengaged. The

Alciclutches maybe of any suitable type although, in

llthe present. showing, disc-clutches are illustrated. The sliding partsor cones 43 and 44 are splined f onrthefsh'aftf38 and are shifted bysuitable yokes, "'aspanbeseen more particularly from Figure 3.

E"Each'oftheclutch heads 39, 40, 4l and 42 have fast"therewith^sgears45, 4S, 41 and 48, respec- `..tiv.ely, .of'ldiierent sizes to eilect theautomatic change speeds desired. The gears 45 and 46 of fclutcl'i heads39 and 40 mesh, respectively, with their mating gears 49 and 50 fast onthe speed input. shaft36fwhile.- thegears 41 and.48 oficlutch heads 44 I1 and. 42=mesh with theirY matingvgears 5|.vand,.52 fasti on.. thespeedoutput :shaft 31. uIt Willberecognized that anyoneof the speed- 25.change operationsrmay be effected automatically bythe selecting devicevI- l 2,y or manually by ,the -liftingof-cer-tain of the keys Kthereof,operably Iconnected through-control: mechanism 214 v(as vshown in 'saidcopending application,` as one exo ample) one to eachof.theconnectors-39,A 40, 4.1-A andY 42S, respectively. lIlhe connectors39c wandiy 4l3.:areA connected to `opposite .arms of a rocker-.arm .298which shifts. the yoke :2.99` to 'engage the clutch :cone .43r'with-either clutch head 'fi-5 39 or 49, respectively and disengage.the other;

whileconnectors- 4land,- 42c4 -areconnected to opposite armsofa.rocker.arm 295 to shift-the yoke 2911to-:engage clutch,=cone.44f.with`either head .4 I- -or i12-and disengage-the other.

-40 The vspindle drive continues from .thefspeed output shaft 31 throughhandfchange `gears. 53 i :and 54 to.-shaft .55. Thesehand-changed gearsare; `respectively, .fast Aon'fthe.- outer lends ofthe 'f shafts 31 and55 so'as .to lbe accessible for quick HA5- manualchangethrough asuitable door inthe. end ed'walls of the head-stock; housing 20in-bearings .l -211and728 (see-Fig.V 3) and isdriven from aconstantspeed motor shaft 3| Yactuated from a -pul- -ley (not shown) .f.or by. an .electric motor. M .sup- :ported onfan end wall. of theheadstockv casing .f 29. The drive from the motorshaft 3i isthrough f agear .32 keyed thereon..and,meshingwithidler gearfc33onishaft-34awhichidler gear. drives, gear 3 35. These. shafts and gearsrun at ,constantspeed ywhile; 'the r machineisl inoperation. From 4.thedriving-gear.35, fthe gearingto..the.. spindle 2l includes four.`automatici speed changes, one pair Yof hand-changedf gears... andshiftable `gearing "for convertingthe machine into a low, or.. highspeedA machine, -allof which. being shownr in eX- --tended arrangementin Fig-ure 3. andthe gearing -for operating vthe .feed shaft.39,;turretfs1ide 23,

-wallv ,of Vthe headstock-casing 20 and. may -be pro- --vided' =ingroups tofobtain different franges' of f vspeeds in a manner and for apurpose well known :inv the art.

From shaft 55the machine may be converted from' a lowspeed .to ahighspeed machine, .and conversely, but always influenced by the speedchangeswhich are; effected: by .the hand-.change gears-53 anda54 andvthrough the automatic l5gclutclf1es rjust' described. By providingshaft .55

.5g high speed gear 512L will, mesh with itsmating gear 59, suchchange-over may be effected. It willbeobseryedthat .gears .58 and 59 arekeyed to a jack-shaft 60 and that gear 59 is in mesh with a 'gear 6l.keyed to asleeve bearing 62 in which the rearend ofthe spindle 2| issplined at 63 for longitudinal adjustment therein. The sleeve bearing62, as is'the shaft 55 and the jack shaft 60, is journaled at 28 inr theheadstock casing 2 0in suitable ball bearings.

Feed shaft drive The'drive for the "feed shaft 39 (which actuates theturret slide 23 and cross slides v25 and 26) is connected directly withthe spindle 2i so that the feed. will always.*beginratio per revolutionof the spindle regardless of the speed of the spindle. This feed driveis taken off of the spindle sleeve $2 (Fig. 3) which has teeth E8 cuttherein meshing With a gear @9. 'The gear t9 is keyed to a jack shaft i9which has a spur gear 59a fast thereto for driving gear 1i keyed to oneend of a stub shaft if which also has gear 'it fast thereon to drivegear 'iii (Fig. e) through the intermediate gear lli. The gear i5 iskeyed to an input speed shaft it which is aligned with and rotatablyindependent of a main or output speed shaft 11 for imparting therequisite movements to the turretslide Z3 and the cross-slides 25.

From this input shaft TG, various feed changes may be obtained throughthe medium of hand" change gears for the tool slides as Well as threeautomatic feed changes of any selected feed obtained by the hand-changegears. As shown in Figures 2 and 4, three separate and independentcounter shafts f8, 'i9 ani 8i! are grouped about the aligned input andoutput shafts 'it and 'il and suitably journaied in the housing 29. Eachof these counter shafts '58, '59, and 89 has rotatably mounted thereon aclutch head 3|, 83 and t5, respectively, each clutch head having amating gear 92, Eid and fast thereon, respectively, which gears are ofdifferent sizes, and mesh, respectively, with a cluster gear fast to themain feed clutch head El! rotatably mounted on the output speed shaftil. The cluster gear comprises three gear members 99, 89 and 99respectively. Also, each of said counter shafts it, 'i9 and Bt* has asliding clutch part or cone 9|, 92 and 93, respectively, splined thereonfor reciprocating into and out of engagement with the clutch heads onsaid counter shafts.

The output shaft 'il has a quick return clutch head gli rotatablymounted thereon and carrying with it a mating gear Sii. The clutch head9d is in opposed cooperative relation with the main feed clutch Si so asto he served by the clutch slide or cone de splined on the shaft l?,whereby one of the clutch heads 'Si or iid Will be engaged when theother is disengaged or both disengaged when the cone is in a neutralposition. The quick return clutch head 9i! is for connecting the shaftl'li with the motor its for effecting quick idle motions of 'the toolslides 23, 25 and 2t and, to this end, its mating gear 95 is driven froma pinion @if fast on the motor shaft 93 through an intermediate gear 99.

The counter-shafts i6, i9, and it are driven from the input shaft l@through hand-change gears (itil, ffii, E33, ltd, |95 and it) splined onthe ends of shafts so that they can be readily removed manually througha suitable opening in the casing 29 to effect various ratio combinationsof speeds between the input shafts it and said counter-shafts in amanner vvell known in the art. With the selection of hand-change gearsshown, the fine or first feed counter-shaft T8 of the feeding mechanismis driven by gears |E3| and |92; the second or intermediate feedcountershaft iii is driven by gears |93 and |04; and the third orcoarser feed counter-shaft 89 is driven by gears E95 and |96, all, asabove stated, are hand-change gears well known in the art.

rfhe three automatic changes of speed of feed of the tool slides areobtained in the following manner:

l. For fine feed of movement of the tool slides and all of the clutchcones 9 I, 92 and 93 being out of engagement with their respectiveclutch heads, the clutch cone 9| is moved into clutching engagement Withthe clutch head 8| and cone 96 is moved into engagement with main feedclutch head 81, thus the drive being from input shaft 'it throughhand-change gears MH, |62, shaft 13, clutch head 8|, gears 82, 88, andmain feed clutch head 31 to output shaft Ti. It may be noted here thatthe clutch cone S5 is in engagement with the main feed clutch head 9iduring all feeding operations and is only moved out of engagementtherewith when it is desired to effect the quick idle movements of thetool slides or when the feed mechanism is hand operated for setting-upor the machine stopped;

2. For the second or intermediate feed of the tool slides, and cones Siand 93 being disengaged from their respective clutch heads, the cone 92is moved in engagement with clutch head 8,3, thus the drive being frominput speed shaft le, through hand-change gears |93, |94, shaft '19,clutch head 83, gears 84, 89, and main feed clutch head Si? to outputshaft l1; and

3. For the third or coarse feed of tool slides and With the clutch cones'it and 'i9 disengaged from their respective clutch heads, clutch cone93 is moved into engagement with clutch head 85, thus the drive beingfrom speed input shaft through hand-change gears |S5, |96, shaft Siiclutch head t5, gears 85, 99, and main feed clutch head 8l to outputshaft It will be recognized that any one of the above describedfeed-change operations may be effected automatically by the selectingdevice l2 or manually by lifting certain of the keys thereof,operatively connected one to each of the connectors Bic, 9N, 83e, 83d,85C and 35d, respectively as disclosed in the aforesaid copendingapplication. The connectors 3|C and tid are connected to opposite arm ofa rocker-arm 342 which shifts the yoke 3M to engage or disengage cone 9|Vwith clutch 8|; connectors i330 and 83d are similarly connected torocker SI5 Which shifts yoke til to engage or disengage cone 52 withclutch 83; and connector 85 and 95d are also similarly connected torocker arm 3|Ei to shift 32@ for engaging or disengaging cone 93 withclutch in like manner the cone 96 is shifted to neutral position or intoengagement with the main feed clutch 8T by connector Sic on one end ofrocker arm $92 and is shifted into engagement With fast motion clutch 9iby connector ed on an opposite arm of rocker-arm 392, which actuates theyoke 394.

The mechanism which operates the clutch cones 9|, 92 and is to beinterloched (as disclosed in said copending application) so that, whenany one of the three clutch cones is operated to engage its clutch theyautomatically disengage any other of said clutch cones that waspreviously in engagement, this being a safety feature which permits onlyone of the three feed clutches to be engaged at one time While the otherclutch heads and their mating gears run idle on their respective shafts.Also, the countershafts "iii, 'i 9 and are rotated continuously from theinput shaft it nough their res estive handchange gears while the machineis in operation.

The fast motion of tl e tool slides 23 and E5 (that is, their idlemotion from the time that any tool then in operation has finishedcutting and is brought back to clear the subject being machined, theturret indexed, and then moved forward to bring the next set of cols tothe subject) is obtained by means of the quick return motor |99, whichruns at constant speed continually during operation of machine, throughpinion Si on motor shaft 93 driving gear 9d meshing with mating;gear195^ofquick return clutch head 9d, which .'ilatterispengagedautomaticaily. by, clutch ycone e5, :"when' it f. disengages themain,feedf clutch *whereby* fast motionY is imparted to output :shaft TI.4-When the tools of theturret slide 23 and/or the crossslides 25 areagainy in position .for cuttingoperationsron the work-subject, quickyreturn clutch et is disengaged and-the main feed clutch Bl isengaged'by the cone S6 whereby shaft 'iis again brought to feedingvmotion. v When lis in operation, cluster Vgear iis-8 E-Ql runs idle onsha t it and shaft 'I6 runs idle in the end'ofy shaft "Ii, as shown.at'pointa.

Fromoutputshait ii, iced or fast motion 'is-transmitted to. thefeedshaft 3d (which operf ates turret slide 25 cross glides 25 and 25)through gear -il'I-loose on shaft "I'i but made fast thereto by means ofa .saiety coupling which comrprises, in the present instance, a shearpin i held in an annular flange .It on one face of gear mi,`and'extending into a disc member IIB-disfposedwith the bushing ISS andkeyed toshaft `If laad --fshear pin H8 breaks through thereby protectingthe mechanisms of the machine. abnormal load-is removed, a new shear pinI TI. Gear -Ii drives gear I iI keyed in feed shaft exceeds normaloperatingV conditions After cause for is inserted and machine is againready for operation.

vvAspecd and feed control device i I 2. enclosed in lthecasingiIEalFigs. 1 and 2), which automati- `'callyncontrols the operations ofall the clutches and therefore theoperationioi .the tool slides inparticular, isalso driven from gear IGT by bevel i gear I lvhaving anadjustable .drive connector, as

at H4, with` thegeard'i, the connector iii being interengaging teeth.orrprejectionsion op- .'posing vfaces of gears ifi? and H3. and held inv,adjusted fixed engagement bythe nut H5 and A shoulder Iit` on shaftTf. Bevel gear Eil keyed .on-worm shaft tit meshes with gear IIS andthus be seen that, by having Vthe gear 'mi rotatable on the shaft ii andcoupled thereto by the shear pin` IGS, the timingbetween the control de-(and thus the turu vice H2 and the feed shaft ret slide) and the crossYslides 25 will not be altered should any overload, jamming or other .iincident occur which would cause the shear pin M8 to break.

As shown in Figures l, 2 and fi, the worm shaft Y IiB is providedon itsouter extremity with a square end i I da to receive ay hand-crank, orother instrument, for hand-cranking the machine for Asetting-up purposesasis well understood in the art.

TOOL SLIDLS As above stated, all movements of the main or turret slide23 and the cross-slides 25 are actuated from the feed shaft it throughworm I d3,

"worm wheel `I5I on shaft E53 having fast thereon i motor. it@ throughgears 523,1 :fwhichilatter is Akeyed on the shaft I2 t.

a single disc-cam 135, which latter is engaged by a cam follower Iliicarried on slide 23 (see Fig. l), all as more particularly shown anddescribed inthe copending application above mentioned.

The clutch control device 271i, as fully described intheaforesaid'letters patent, or any auxiliary equipment, may be driven fromthe quick return 2d, |27, and 28,

1rial-Iavng thus; described theinvention'inthe manner in which it isto-be performed, it is to be understood. .that the preciseconstructionand and, in-otherinstances, more specifically.

That which is claimed, as new, is:

l. Inl a machine having operable parts, the improvement comprising avtransmission mechanism between said parts and having a main shaftconnected with one of said operable parts, clutchhead rotatably mountedon said main shaft, a shiftable clutch-member splined on said main shaftto `engage and disengage said clutch head,

a. clusterv gear rotatable with said clutch-head .about-said main-shaft,a plurality of countershafts; disposed about said main shaft and eachhaving a clutch-head rotatably mounted thereon and carrying a gearmeshing with one of said gears respectively of said cluster gear, ashiftable clutchmember on each of said countershafts respectively andsplined thereto to engage or disengage its respective clutch head, agear fast on each of said countershafts respectively, an auxiliaryrotatable shaft aligned with one end of said main shaft and having aplurality of gears fast-thereon and leach meshing with said gearsrespectively on said countershafts, and a gear connection between saidother of said operable parts and said auxiliary shaft, the gearconnections between said cluster gear and each of said countershaftsbeing of diierent ratios and the gear connections between each of saidcountershafts and said other operable part being of different ratios,means for operating said shiftable clutch-members whereby to vary therate of movement of said operable part connected with said main shaft.

2. In a machine having a driving part and another part to be moved fromsaid driving part for certain of its movements, the improvementcomprising a, transmission mechanism having a main shaft operablyconnected with said movable parts, a pair of spaced clutch-headsrotatably mounted on said main shaft, a shiftable clutchmember or conesplined on said main shaft and interposed between said clutch-heads toengage one and release the other and to assume a neutral position,a'cluster gear rotatable with one of said clutch heads about saidvshaft,a plurality of countershafts disposed about said main shaft and eachhaving a clutch-head rotatably mounted thereon and vcarrying a gearmeshing with :one Vof said gears respectively of said cluster gear, ashiftable Yclutch member or cone on each of saidv countershaftsrespectively and splined thereto to vengage or disengage its respectiveclutch head, a gear fasten each of said countershafts respectively anddriven from said driving part,` the gear connections between saidcluster gear and each of said countershafts being or" ldifferent ratiosand the gear connections between each of said countershafts and saiddriving part beingY of different ratios whereby the rate of movement ofsaid movable part may be varied When driven from said driving part, amotor in constant operative connection with the other of saidclutch-heads on said main shaft to drive said main shaft to move saidmovable parts for other of'its movements when said clutch head isenygaged,k and `means forA shifting said shiftable clutch-members.

3. In a machine,v having a driven part and a slide .to be.. fed;l in4one direction. of` movement @i from said driven part, the improvementcomprising a feed-change transmission mechanism having a main shaft, apair of spaced clutch-heads rotatably mounted on said main shaft, ashiftable clutch-member splined on said main shaft and interposedbetween said clutch-heads to engage one and release the other and toassume a neutral position, a cluster gear rotatable with one of saidclutch-heads about said main shaft, a plurality of countershaftsdisposed about said main shaft and each having a clutch-head rotatablymounted thereon and carrying a gear meshing with one of said gears,respectively, of said cluster gear, a shiftable clutch-member on eachor" said countershafts, respectively, and splined thereto to engage ordisengage its respective clutch-head, an auxiliary rotatable shaftaligned with one end of said main shaft and having a plurality of gearsfast thereon, a gear fast on each of said countershafts, respectively,and meshing with one of said gears on said auxiliary shaft, a gearconnection between said driven part and said auxiliary shaft, the gearconnections between said cluster gear and each of said countershaftsbeing of diierent ratios and the gear connections between each of saidcountershats and said auxiliary shaft being oi different ratios, a feedshaft operatively connected with said slide, a gear connection betweensaid feed shaft and said main shaft and including a breakable overloadmeans, and a motor in constant operative connection with the other ofsaid clutch-heads on said main shaft to drive said main shaft for otheroperations of said slide when said clutch head is engaged, and means forshifting said shiftable clutch-members.

WILLIAM WALLACE POTTER.

ALFRED JOSEPH FULLER.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 2,255,739 Curtis n Sept. 9, 1941 2,280,683 Bedford Apr. 21,1942

